[postgis-users] Handling N-d arrays in PostGIS
Antonio Rodriges
antonio.rrz at gmail.com
Mon Oct 30 09:55:02 PDT 2017
Paul,
I suppose POINTM is the solution to get the data somehow into PostGIS but I
will have a handful of options to process them and millions of rows with
points,
PostGIS has raster data type tailored to 2-d arrays (please, correct me if
I am wrong):
https://postgis.net/docs/RT_reference.html
http://postgis.net/docs/manual-2.2/using_raster_dataman.html
Therefore, I seek a way to import a 3-d array and be able to apply the
functionality described in the links above
Antonio
2017-10-30 15:25 GMT+03:00 Paul Ramsey <pramsey at cleverelephant.ca>:
> As others have noted, a POINTM or MULTIPOINTM will serve to store your
> data just fine, but what you plan to *do* with that data after will
> determine whether a relational database is really the correct tool for you.
>
> ATB,
> P
>
> On Mon, Oct 30, 2017 at 4:56 AM, Antonio Rodriges <antonio.rrz at gmail.com>
> wrote:
>
>> I suppose it has a bit different purpose (like an efficient handling of
>> sparsity which is not the case with dense climate data) and I hope there is
>> an easier solution (I just have 3 dimensions...)
>>
>> Antonio
>>
>> 2017-10-30 14:52 GMT+03:00 Stephen V. Mather <svm at clevelandmetroparks.com
>> >:
>>
>>> Ya, I’m not sure point clouds are at all the fix. They just address the
>>> dimensionality question well, though not the gridded data requirement.
>>>
>>> Cheers,
>>> Best,
>>> Steve
>>>
>>>
>>> [image: http://sig.cmparks.net/cmp-ms-90x122.png]*Stephen V. Mather*
>>> GIS Manager
>>> (216) 635-3243 (Work)
>>> (216) 339-6347 (Cell)
>>> --sent from phone--
>>>
>>>
>>>
>>> On Oct 30, 2017, at 07:49, Antonio Rodriges <antonio.rrz at gmail.com>
>>> wrote:
>>>
>>> Thank you for pointing to this tool.
>>>
>>> However, I thought that since PostGIS uses GDAL it may be easier to
>>> import such arrays, e.g. just split them onto individual 2-d grids (since
>>> PostGIS mainly understands 2-d grids).
>>>
>>> 2017-10-30 14:34 GMT+03:00 Stephen V. Mather <
>>> svm at clevelandmetroparks.com>:
>>>
>>>> I don’t know if it’s the ideal tool for the job, as it’s more flexible
>>>> than you need, not being a regularized grid but a point cloud, but you
>>>> might look to the pgPointCloud extension: https://github.com/
>>>> pgpointcloud/pointcloud
>>>>
>>>> Cheers,
>>>> Best,
>>>> Steve
>>>>
>>>>
>>>> [image: http://sig.cmparks.net/cmp-ms-90x122.png]*Stephen V. Mather*
>>>> GIS Manager
>>>> (216) 635-3243 (Work)
>>>> (216) 339-6347 (Cell)
>>>> --sent from phone--
>>>>
>>>>
>>>>
>>>> On Oct 30, 2017, at 07:09, Antonio Rodriges <antonio.rrz at gmail.com>
>>>> wrote:
>>>>
>>>> Hello,
>>>>
>>>> Thank you for the reply, however my data is slightly different. Sorry
>>>> that I did not make it clearer at the very beginning.
>>>>
>>>> Actually I would like to import a dense, 3-d array of wind speed (a
>>>> time series of grids, each grid point contains the wind speed value)
>>>>
>>>> The array is stored as a NetCDF file
>>>> FIles are here https://www.esrl.noaa.gov/psd/
>>>> cgi-bin/db_search/DBListFiles.pl?did=61&tid=59909&vid=4298
>>>>
>>>> The size of the array and its dimensions are below
>>>>
>>>> dimensions:
>>>> lat = 94 ;
>>>> lon = 192 ;
>>>> time = 1460;
>>>>
>>>> The array
>>>>
>>>> short uwnd(time,lat,lon) ;
>>>> uwnd:long_name = "6-Hourly Forecast of U-wind at 10 m" ;
>>>> uwnd:valid_range = -32765s, -8765s ;
>>>> uwnd:unpacked_valid_range = -120.f, 120.f ;
>>>> uwnd:actual_range = -38.2f, 38.07f ;
>>>> uwnd:units = "m/s" ;
>>>> uwnd:add_offset = 207.65f ;
>>>> uwnd:scale_factor = 0.01f ;
>>>> uwnd:missing_value = 32766s ;
>>>> uwnd:_FillValue = -32767s ;
>>>> uwnd:precision = 2s ;
>>>> uwnd:least_significant_digit = 1s ;
>>>> uwnd:GRIB_id = 33s ;
>>>> uwnd:GRIB_name = "U GRD" ;
>>>> uwnd:var_desc = "u-wind" ;
>>>> uwnd:dataset = "NCEP/DOE AMIP-II Reanalysis (Reanalysis-2)" ;
>>>> uwnd:level_desc = "10 m" ;
>>>> uwnd:statistic = "Individual Obs" ;
>>>> uwnd:parent_stat = "Other" ;
>>>> uwnd:standard_name = "eastward_wind" ;
>>>>
>>>> 2017-10-30 11:04 GMT+03:00 Giuseppe Broccolo <g.broccolo.7 at gmail.com>:
>>>>
>>>> Hi Antonio,
>>>>
>>>>
>>>> 2017-10-29 12:31 GMT+01:00 Antonio Rodriges <antonio.rrz at gmail.com>:
>>>>
>>>>
>>>> Hello,
>>>>
>>>>
>>>> Whether PostGIS allow importing 3-d, 4-d, etc. arrays or only 2-d
>>>> arrays?
>>>>
>>>>
>>>> Specifically, I have a 3-d array with axes (time, lat, lon).
>>>>
>>>> Does this mean that I need to split it onto 2-d bands (lat, lon) and
>>>>
>>>> import the number of bands that is equal to the number of time steps
>>>>
>>>> in the 3-d array?
>>>>
>>>>
>>>>
>>>> Which is the data source from which you import the data (e.g. textual,
>>>>
>>>> etc.)?
>>>>
>>>>
>>>> If I've correctly understood, you have arrays where geospatial and
>>>>
>>>> non-geospatial information
>>>>
>>>> is present, each one providing a "dimension" of the array.
>>>>
>>>>
>>>> Just FYI, in PostGIS is possible to define mixed, structured data with
>>>>
>>>> constructors like POINTM
>>>>
>>>> and POINT, that allow to add a further dimension to the 2D/3D
>>>> (respectively)
>>>>
>>>> geospatial ones, that
>>>>
>>>> includes a scalar information.
>>>>
>>>>
>>>> Hope this can help in your import, otherwise provide more information
>>>> about
>>>>
>>>> source data and how
>>>>
>>>> you'd like to import.
>>>>
>>>>
>>>> Giuseppe.
>>>>
>>>>
>>>>
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